This invention relates to integrated optics and, more particularly, to optical modulators and methods of modulating light.
In integrated optics, thin film technology is employed in optical circuits and devices to achieve more efficient, more economical and minute circuitry. In integrated optic wave guides, modulators and the like, a thin optical wave guide in the form of a light-propagating thin film, which may be only a few microns in thickness, is supported upon a rigid substrate, such as glass. In order to propagate light, the film must have an index of refraction greater than that of the substrate and any other material in contact with the film, such as air. When this condition occurs, the light entering the film will be reflected between the film surfaces and retained in and guided along the film.
It is advantageous to modulate the light propagated through the wave guide film in some aspect, for example intensity, mode, frequency, etc. Such modulation varies some characteristic or property of the light that is discharged from the wave guide film so that it may carry information. Thus, in integrated optics, modulators are valuable in many applications.
Several forms of optical modulators are presently known. In the present optical modulators, the principal effect that produces the modulation is a change in the dielectric properties of the materials in response to electric or magnetic fields or mechanical stresses. Such modulators may employ liquid or solid crystal materials, liquids or gases as light propagating materials. In contrast to prior modulators, the optical modulator and method of the present invention achieves modulation by the physical deformation of the light propagating film directly with a force which is impressed on or across the propagating material. The light propagating material of the present invention is preferably formed of a thin polymeric elastomer film and this film is preferably deformed by an electric field so as to effect a change in the cross section of the thin film. Such changes in cross section result in modulation of the light by scattering or diffracting all or part of the light propagated by the film at the location of the deformation.
In one principal aspect of the present invention, an optical modulator comprises an optical wave guide formed of a deformable material of a given thickness. Deforming means exerts a force on the material to physically deform the deformable material to cause a change in the cross section of the material which cross section change modulates the light by scattering or diffraction at the deformation.
In still another principal aspect of the present invention, an optical wave guide comprises a film of a deformable elastomer or thermoplastic at or near its glass transition temperature which is transparent to the light to be propagated and a rigid substrate supporting the film, which substrate has an index of refraction lower than that of the film.
In still another principal aspect of the present invention, a method of modulating light includes guiding light along an optical wave guide of predetermined cross section and in a direction perpendicular to cross section, and changing the predetermined cross section of the wave guide by impressing a force thereon to physically deform the wave guide to change the predetermined cross section to modulate the light by scattering or diffraction at the deformation.
These and other objects, features and advantages of the present invention will be more clearly understood through a consideration of the following detailed description.